RISC-V: Add PE/COFF header for EFI stub

Linux kernel Image can appear as an EFI application With appropriate
PE/COFF header fields in the beginning of the Image header. An EFI
application loader can directly load a Linux kernel Image and an EFI
stub residing in kernel can boot Linux kernel directly.

Add the necessary PE/COFF header.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Link: https://lore.kernel.org/r/20200421033336.9663-3-atish.patra@wdc.com
[ardb: - use C prefix for c.li to ensure the expected opcode is emitted
       - align all image sections according to PE/COFF section alignment ]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

diff --git a/arch/riscv/include/asm/sections.h b/arch/riscv/include/asm/sections.h
new file mode 100644 (file)
index 0000000..3a9971b
--- /dev/null
+++ b/arch/riscv/include/asm/sections.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ */
+#ifndef __ASM_SECTIONS_H
+#define __ASM_SECTIONS_H
+
+#include <asm-generic/sections.h>
+
+extern char _start[];
+extern char _start_kernel[];
+
+#endif /* __ASM_SECTIONS_H */

diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi-header.S
new file mode 100644 (file)
index 0000000..8e733aa
--- /dev/null
+++ b/arch/riscv/kernel/efi-header.S
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ * Adapted from arch/arm64/kernel/efi-header.S
+ */
+
+#include <linux/pe.h>
+#include <linux/sizes.h>
+
+       .macro  __EFI_PE_HEADER
+       .long   PE_MAGIC
+coff_header:
+#ifdef CONFIG_64BIT
+       .short  IMAGE_FILE_MACHINE_RISCV64              // Machine
+#else
+       .short  IMAGE_FILE_MACHINE_RISCV32              // Machine
+#endif
+       .short  section_count                           // NumberOfSections
+       .long   0                                       // TimeDateStamp
+       .long   0                                       // PointerToSymbolTable
+       .long   0                                       // NumberOfSymbols
+       .short  section_table - optional_header         // SizeOfOptionalHeader
+       .short  IMAGE_FILE_DEBUG_STRIPPED | \
+               IMAGE_FILE_EXECUTABLE_IMAGE | \
+               IMAGE_FILE_LINE_NUMS_STRIPPED           // Characteristics
+
+optional_header:
+#ifdef CONFIG_64BIT
+       .short  PE_OPT_MAGIC_PE32PLUS                   // PE32+ format
+#else
+       .short  PE_OPT_MAGIC_PE32                       // PE32 format
+#endif
+       .byte   0x02                                    // MajorLinkerVersion
+       .byte   0x14                                    // MinorLinkerVersion
+       .long   __pecoff_text_end - efi_header_end      // SizeOfCode
+       .long   __pecoff_data_virt_size                 // SizeOfInitializedData
+       .long   0                                       // SizeOfUninitializedData
+       .long   __efistub_efi_pe_entry - _start         // AddressOfEntryPoint
+       .long   efi_header_end - _start                 // BaseOfCode
+#ifdef CONFIG_32BIT
+       .long  __pecoff_text_end - _start               // BaseOfData
+#endif
+
+extra_header_fields:
+       .quad   0                                       // ImageBase
+       .long   PECOFF_SECTION_ALIGNMENT                // SectionAlignment
+       .long   PECOFF_FILE_ALIGNMENT                   // FileAlignment
+       .short  0                                       // MajorOperatingSystemVersion
+       .short  0                                       // MinorOperatingSystemVersion
+       .short  LINUX_EFISTUB_MAJOR_VERSION             // MajorImageVersion
+       .short  LINUX_EFISTUB_MINOR_VERSION             // MinorImageVersion
+       .short  0                                       // MajorSubsystemVersion
+       .short  0                                       // MinorSubsystemVersion
+       .long   0                                       // Win32VersionValue
+
+       .long   _end - _start                           // SizeOfImage
+
+       // Everything before the kernel image is considered part of the header
+       .long   efi_header_end - _start                 // SizeOfHeaders
+       .long   0                                       // CheckSum
+       .short  IMAGE_SUBSYSTEM_EFI_APPLICATION         // Subsystem
+       .short  0                                       // DllCharacteristics
+       .quad   0                                       // SizeOfStackReserve
+       .quad   0                                       // SizeOfStackCommit
+       .quad   0                                       // SizeOfHeapReserve
+       .quad   0                                       // SizeOfHeapCommit
+       .long   0                                       // LoaderFlags
+       .long   (section_table - .) / 8                 // NumberOfRvaAndSizes
+
+       .quad   0                                       // ExportTable
+       .quad   0                                       // ImportTable
+       .quad   0                                       // ResourceTable
+       .quad   0                                       // ExceptionTable
+       .quad   0                                       // CertificationTable
+       .quad   0                                       // BaseRelocationTable
+
+       // Section table
+section_table:
+       .ascii  ".text\0\0\0"
+       .long   __pecoff_text_end - efi_header_end      // VirtualSize
+       .long   efi_header_end - _start                 // VirtualAddress
+       .long   __pecoff_text_end - efi_header_end      // SizeOfRawData
+       .long   efi_header_end - _start                 // PointerToRawData
+
+       .long   0                                       // PointerToRelocations
+       .long   0                                       // PointerToLineNumbers
+       .short  0                                       // NumberOfRelocations
+       .short  0                                       // NumberOfLineNumbers
+       .long   IMAGE_SCN_CNT_CODE | \
+               IMAGE_SCN_MEM_READ | \
+               IMAGE_SCN_MEM_EXECUTE                   // Characteristics
+
+       .ascii  ".data\0\0\0"
+       .long   __pecoff_data_virt_size                 // VirtualSize
+       .long   __pecoff_text_end - _start              // VirtualAddress
+       .long   __pecoff_data_raw_size                  // SizeOfRawData
+       .long   __pecoff_text_end - _start              // PointerToRawData
+
+       .long   0                                       // PointerToRelocations
+       .long   0                                       // PointerToLineNumbers
+       .short  0                                       // NumberOfRelocations
+       .short  0                                       // NumberOfLineNumbers
+       .long   IMAGE_SCN_CNT_INITIALIZED_DATA | \
+               IMAGE_SCN_MEM_READ | \
+               IMAGE_SCN_MEM_WRITE                     // Characteristics
+
+       .set    section_count, (. - section_table) / 40
+
+       .balign 0x1000
+efi_header_end:
+       .endm

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 703e59d..11e2a4f 100644 (file)
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -12,6 +12,7 @@
 #include <asm/csr.h>
 #include <asm/hwcap.h>
 #include <asm/image.h>
+#include "efi-header.S"
 
 __HEAD
 ENTRY(_start)
@@ -21,10 +22,18 @@ ENTRY(_start)
         * Do not modify it without modifying the structure and all bootloaders
         * that expects this header format!!
         */
+#ifdef CONFIG_EFI
+       /*
+        * This instruction decodes to "MZ" ASCII required by UEFI.
+        */
+       c.li s4,-13
+       j _start_kernel
+#else
        /* jump to start kernel */
        j _start_kernel
        /* reserved */
        .word 0
+#endif
        .balign 8
 #if __riscv_xlen == 64
        /* Image load offset(2MB) from start of RAM */
@@ -42,7 +51,14 @@ ENTRY(_start)
        .ascii RISCV_IMAGE_MAGIC
        .balign 4
        .ascii RISCV_IMAGE_MAGIC2
+#ifdef CONFIG_EFI
+       .word pe_head_start - _start
+pe_head_start:
+
+       __EFI_PE_HEADER
+#else
        .word 0
+#endif
 
 .align 2
 #ifdef CONFIG_MMU

diff --git a/arch/riscv/kernel/image-vars.h b/arch/riscv/kernel/image-vars.h
new file mode 100644 (file)
index 0000000..8c212ef
--- /dev/null
+++ b/arch/riscv/kernel/image-vars.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ * Linker script variables to be set after section resolution, as
+ * ld.lld does not like variables assigned before SECTIONS is processed.
+ * Based on arch/arm64/kerne/image-vars.h
+ */
+#ifndef __RISCV_KERNEL_IMAGE_VARS_H
+#define __RISCV_KERNEL_IMAGE_VARS_H
+
+#ifndef LINKER_SCRIPT
+#error This file should only be included in vmlinux.lds.S
+#endif
+
+#ifdef CONFIG_EFI
+
+/*
+ * The EFI stub has its own symbol namespace prefixed by __efistub_, to
+ * isolate it from the kernel proper. The following symbols are legally
+ * accessed by the stub, so provide some aliases to make them accessible.
+ * Only include data symbols here, or text symbols of functions that are
+ * guaranteed to be safe when executed at another offset than they were
+ * linked at. The routines below are all implemented in assembler in a
+ * position independent manner
+ */
+__efistub_memcmp               = memcmp;
+__efistub_memchr               = memchr;
+__efistub_memcpy               = memcpy;
+__efistub_memmove              = memmove;
+__efistub_memset               = memset;
+__efistub_strlen               = strlen;
+__efistub_strnlen              = strnlen;
+__efistub_strcmp               = strcmp;
+__efistub_strncmp              = strncmp;
+__efistub_strrchr              = strrchr;
+
+#ifdef CONFIG_KASAN
+__efistub___memcpy             = memcpy;
+__efistub___memmove            = memmove;
+__efistub___memset             = memset;
+#endif
+
+__efistub__start               = _start;
+__efistub__start_kernel                = _start_kernel;
+__efistub__end                 = _end;
+__efistub__edata               = _edata;
+__efistub_screen_info          = screen_info;
+
+#endif
+
+#endif /* __RISCV_KERNEL_IMAGE_VARS_H */

diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index f3586e3..9795359 100644 (file)
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -10,6 +10,7 @@
 #include <asm/cache.h>
 #include <asm/thread_info.h>
 #include <asm/set_memory.h>
+#include "image-vars.h"
 
 #include <linux/sizes.h>
 OUTPUT_ARCH(riscv)
@@ -17,6 +18,9 @@ ENTRY(_start)
 
 jiffies = jiffies_64;
 
+PECOFF_SECTION_ALIGNMENT = 0x1000;
+PECOFF_FILE_ALIGNMENT = 0x200;
+
 SECTIONS
 {
        /* Beginning of code and text segment */
@@ -67,6 +71,11 @@ SECTIONS
                _etext = .;
        }
 
+#ifdef CONFIG_EFI
+       . = ALIGN(PECOFF_SECTION_ALIGNMENT);
+       __pecoff_text_end = .;
+#endif
+
        /* Start of data section */
        _sdata = .;
        RO_DATA(SECTION_ALIGN)
@@ -83,16 +92,26 @@ SECTIONS
        .sdata : {
                __global_pointer$ = . + 0x800;
                *(.sdata*)
-               /* End of data section */
-               _edata = .;
        }
 
+#ifdef CONFIG_EFI
+       .pecoff_edata_padding : { BYTE(0); . = ALIGN(PECOFF_FILE_ALIGNMENT); }
+       __pecoff_data_raw_size = ABSOLUTE(. - __pecoff_text_end);
+#endif
+
+       /* End of data section */
+       _edata = .;
+
        BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
 
        .rel.dyn : {
                *(.rel.dyn*)
        }
 
+#ifdef CONFIG_EFI
+       . = ALIGN(PECOFF_SECTION_ALIGNMENT);
+       __pecoff_data_virt_size = ABSOLUTE(. - __pecoff_text_end);
+#endif
        _end = .;
 
        STABS_DEBUG